Bad air originating in tank and not compressor

[grf88]

I posted this in response to a thread talking about sources of CO in breathing gas but decided to post in the Accidents and Incidents Forum as the results could have been serious:

I have just returned from a trip to the Caribbean and I am really glad that I took my Analox CO analyzer there. The resort has always provided clean air and just recently installed a new compressor and bought new steel tanks. First day of diving I tested my own tank and as expected it read 0 ppm. I gave the analyzer to my son to test his own tank. He called out and said his tank was reading 75 ppm so I assumed he had done something wrong and upset the calibration. I re-calibrated it to ambient air and then went to show him what he did wrong. Meter read 81 ppm which I thought was damned near impossible so I tested my own tank again and every other tank that was set up for the divers. Sure enough none of the other tanks registered more than 1 ppm. Tested my son's tank yet again and it still read 81 ppm, replaced his tank with a new one and set the contaminated tank to drain. When the interior of the tank was inspected they found 3" of seawater and a great deal of rust, somehow the tank had drained and had must of taken on seawater when being swum in from the boat. Hate to think of what would have happened if my son had used the tank. It also goes to show that an inline tester on the compressor would not have prevented this incident. I have vowed to test every tank that I, my son or my dive buddies dives regardless of the reliability of the source. I am sure that the other divers that were present will be in the market for an CO analyzer.

 

[Dr. Lecter]

Yikes. Thanks for sharing. Was it a steel tank, or is rust shorthand for whatever mess seawater plus aluminum corrosion creates?

 

[grf88]

This was a steel tank approximately 4 months old.

 

[Peter_C]

Glad you tested the tank as that is a lot of CO for a tank.

On the other hand where did the CO come from? Some quick research on rust does not show it produces CO??
Rust - Wikipedia, the free encyclopedia

---------- Post added August 14th, 2014 at 10:48 PM ----------

Hmmm...

Fe2O3 + 3CO = 2Fe + 3CO2

Iron(III) oxide - Wikipedia, the free encyclopedia

 

[victor]

Interesting. If he had dived the tank then the results might have depended on how he decends.
Me I am head down, feet up, water in the neck of the tank, flooded first stage, no air to breathe, OOA situation, aborted dive.
A begineer, weighted heavy, vertical descent standing up, dive at 45 degrees, breathing CO at 81 ppm, stressed, headache from CO, confused, could have been very bad news.

Lucky you tested.
[h=2]From Carbon Monoxide Questions and Answers | CPSC.gov
What CO level is dangerous to my health?[/h]The health effects of CO depend on the CO concentration and length of exposure, as well as each individual's health condition. CO concentration is measured in parts per million (ppm). Most people will not experience any symptoms from prolonged exposure to CO levels of approximately 1 to 70 ppm but some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms become more noticeable and can include headache, fatigue and nausea. At sustained CO concentrations above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.

 

[chillyinCanada]

How is it that no divers of this tank beforehand ran into any difficulty? Did the tank suddenly bloom?

 

[vincent54]

Was the air in tank tested with a different meter? It could have been a faulty instrument. Calibrating wouldn't do any good. Too bad another meter wasn't available to cross check. Better safe than dead. Cheers

 

[DandyDon]

I didn't know that rust could produce CO, and I have certainly read a lot about CO risks & scuba, but maybe so. Yay or nay, the testing was extensive and the 81 ppm was there so it's great that he could, did, and protected his son from a horrible dive.

This really drives home the need to test each and every tank regardless of what you think you know about the provider, compressor, etc. Testing tanks gets boring when you keep getting all zeroes, I know - until you find your first significant reading. Then it all becomes very worthwhile. Compressors should all have CO monitors with auto shut off, but while only a few do - that's only the first step in ensuring clean air.

A begineer, weighted heavy, vertical descent standing up, dive at 45 degrees, breathing CO at 81 ppm, stressed, headache from CO, confused, could have been very bad news.

Lucky you tested.
From Carbon Monoxide Questions and Answers | CPSC.gov
What CO level is dangerous to my health?

The health effects of CO depend on the CO concentration and length of exposure, as well as each individual's health condition. CO concentration is measured in parts per million (ppm). Most people will not experience any symptoms from prolonged exposure to CO levels of approximately 1 to 70 ppm but some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms become more noticeable and can include headache, fatigue and nausea. At sustained CO concentrations above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.

At one atmosphere, sure 81 ppm could make you ill. At 3, 4, or 5 atmospheres of pressure - much damned worse. There are good reasons for why even our liberal US guidelines require CO be less than 10 ppm for scuba, and many countries have lowered their limits to 5 or even 3 ppm.

And it's not just the multiplier effect. CO binds with red blood cells preventing O2 from being as efficiently conveyed to the body, most importantly perhaps to the brain, and it tends to stay bound! The initial damage is offset somewhat descending as PPO also increases, but the worst risk is on the ascent when PPO decreases much faster than the CO bound to the blood. This is why non-diving CO injuries are treated in Hyperbaric chambers. More exactly...

Carbon monoxide mainly causes adverse effects in humans by combining with hemoglobin to form carboxyhemoglobin (HbCO) in the blood. This prevents hemoglobin from releasing oxygen in tissues, effectively reducing the oxygen-carrying capacity of the blood, leading to hypoxia. Additionally, myoglobin and mitochondrial cytochrome oxidase are thought to be adversely affected. Carboxyhemoglobin can revert to hemoglobin, but the recovery takes time because the HbCO complex is fairly stable.

So if ascending with CO tainted air can kill you, but not ascending can kill you, what are your best choices...?!

Fire departments have lower maximums even for their units used at 1 atmosphere, in part because there should be none - so if a compressor allows any CO in, what else could it be allowing in?

Was the air in tank tested with a different meter? It could have been a faulty instrument. Calibrating wouldn't do any good. Too bad another meter wasn't available to cross check. Better safe than dead. Cheers

Do you know much about the Analox EII CO tank tester? Ever used one. I think everything you stated is incorrect. He field calibrated with the dial and sounds like his testing was extensive. The unit would have to be operating very well to read the same 81 ppm before & after testing the other tanks at zero. The only step he did not mention that is suggested by the company is to bump test every day to ensure that it is indeed working, before field calibrating. That's as easy as removing the flow restrictor and blowing in it as everyone's bodies produce some CO. For more significant results, get a smoker (not smoking at the time, but recently) to blow in it.

Getting a 1 ppm reading is nothing really, as we are measuring very small degrees rounded to the nearest ppm. It's amazing that we have this technology available now, at affordable costs.

 

[grf88]

Glad you tested the tank as that is a lot of CO for a tank.

On the other hand where did the CO come from? Some quick research on rust does not show it produces CO??
Rust - Wikipedia, the free encyclopedia

---------- Post added August 14th, 2014 at 10:48 PM ----------

Hmmm...

Fe2O3 + 3CO = 2Fe + 3CO2

Iron(III) oxide - Wikipedia, the free encyclopedia

That is what I would like to know, maybe the Carbon content of the steel is enough or possibly the CO sensor responds to other contaminants

Interesting. If he had dived the tank then the results might have depended on how he decends.
Me I am head down, feet up, water in the neck of the tank, flooded first stage, no air to breathe, OOA situation, aborted dive.
A begineer, weighted heavy, vertical descent standing up, dive at 45 degrees, breathing CO at 81 ppm, stressed, headache from CO, confused, could have been very bad news.

Lucky you tested.
From Carbon Monoxide Questions and Answers | CPSC.gov
What CO level is dangerous to my health?

The health effects of CO depend on the CO concentration and length of exposure, as well as each individual's health condition. CO concentration is measured in parts per million (ppm). Most people will not experience any symptoms from prolonged exposure to CO levels of approximately 1 to 70 ppm but some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms become more noticeable and can include headache, fatigue and nausea. At sustained CO concentrations above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.

My son typically descends horizontal. There was no O2 analyzer available so we could not tell how much Oxygen had been consumed by the rusting process. The first dive was to 87 feet which would probably have made matters worse.

How is it that no divers of this tank beforehand ran into any difficulty? Did the tank suddenly bloom?

This is not a busy dive resort, in between large groups they can go weeks without any more than a couple of divers so it is possible the tank was not being used for a number of weeks.

Was the air in tank tested with a different meter? It could have been a faulty instrument. Calibrating wouldn't do any good. Too bad another meter wasn't available to cross check. Better safe than dead. Cheers

I checked the analyzer on site by blowing into it and getting a 1 ppm and checked it again at home with a tank with known 17 ppm and it is working fine.

 

[dalaimama]

Glad you tested the tank as that is a lot of CO for a tank.

I can't tell you how glad I am that he tested it. I'm also glad that the one person with a CO tester was given the only contaminated tank. If it had been given to anyone else, things might have ended differently.